Saturn spacecraft prepares to meet Titan

Tuesday, 26 October 2004Reuters

The Cassini spacecraft is about to have its closest encounter with the Saturn moon Titan. This colourised image, taken earlier this year, shows the moon with a purple stratospheric haze (Image: NASA/JPL/SSI)

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The Cassini spacecraft has cut off communications with controllers as it prepares to peer beneath a veil of smog shrouding Saturn's moon Titan.

The NASA spacecraft is set to pass within 1200 kilometres of Titan's surface in the early hours of Wednesday morning, Australian time.

It would be the closest pass ever to the mysterious icy moon, whose atmosphere scientists have likened to a primordial Earth.

Cassini will snap infrared and radar images 100 times sharper than any taken so far of Titan, said scientists at NASA's Jet Propulsion Laboratory in Pasadena, California.

Carrying the European Space Agency probe called Huygens, Cassini is supposed to resume contact with NASA controllers later on Wednesday, Australian time.

It will download data and images collected during its pass near Titan, one of 45 planned for the spacecraft's four-year tour of Saturn and its moons.

Titan is the solar system's second largest moon, after Jupiter's Ganymede, and is the only known moon with an atmosphere. Titan is believed to have oceans of liquid methane and ethane on its frozen surface and a nitrogen-rich atmosphere that may hold clues to how Earth's atmosphere evolved.

"What we've got is a very primitive atmosphere that has been preserved for 4.6 billion years. Titan gives us the chance for cosmic time travel ... going back to the very earliest days of Earth when it had a similar atmosphere," said Toby Owens, principal scientist at the Jet Propulsion Laboratory.

In January, Cassini is expected to drop off the Huygens probe. If it survives a parachute-assisted descent through Titan's atmosphere, Huygens is expected to transmit data for several minutes before freezing in temperatures of -178°C, or sinking beneath a lake of methane.

Little is known about Titan's surface and the first hazy images returned by Cassini in July gave little indication of what Huygens may find.

"On this pass we are looking at the area of Titan where the probe will look in much more detail" with photos that can pick out features the size of a football field, said Earl Maize, deputy program manager for the Cassini-Huygens mission.

Scientists do not expect to find signs of life but are interested in chemical reactions taking place in a landscape they theorise looks like a melted ice cream sundae.